Propeller walk is the term for a propeller's tendency to rotate a boat as well as accelerating it forwards or backwards.
A right-handed propeller (which rotates clockwise [as viewed from the stern] when in forward gear) will tend to push the stern of the boat to starboard, thereby pushing the bow to port and turning the boat counter-clockwise unless the rotation is corrected for.. When in reverse gear, the effect will be much greater and opposite. A right-handed propeller run in reverse will push the aft of the boat to port.
Knowing of and understanding propeller walk is important when maneuvering in small spaces. It can be used to one's advantage while mooring off, or it can complicate a maneuver if the effect works against the pilot.
Propeller walk is caused by a difference in the overall force of one side of a propeller due to the angle of the propeller shaft versus the direction of travel. When a propeller shaft is perfectly aligned with the direction of travel there is no propeller walk.
Other terms for propeller walk are:
- propeller effect
- paddle wheel effect
- asymmetric thrust - see Critical engine
- asymmetric blade effect
- transverse thrust
- or simply prop walk.
- "Prop Walk. An explanation of its causes and effect." (PDF). Castle Marine Ltd. Inland Waterways Cruising School. 2004. Retrieved 24 December 2016.
Dand. I. W.: “Hydrodynamic Aspects of Shallow Water Collisions” Transactions of the Royal Institution of Naval Architects, Volume 118, 1976.